This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A157883 #28 Jun 26 2025 12:39:15
%S A157883 1,-1,-11,3,91,-43,-12347,1183,62851,-54423,-39448591,3799763,
%T A157883 27287144401,-375591203,-34562009741,49954996743,89299092717107,
%U A157883 -8604866798383,-135379643536733633,1863607913992123,2694379428323830241,-495661415843787963,-1648224141847799919403
%N A157883 Numerator of Bernoulli(n, 2/5).
%C A157883 From _Wolfdieter Lang_, Jul 05 2017: (Start)
%C A157883 a(n) gives also the numerators of the generalized Bernoulli numbers B[5,2](n) = 5^n*Bernoulli(n, 2/5) with the Bernoulli polynomials B(n, x) = Bernoulli(n, x) from A196838/A196839 or A053382/A053383. For the denominators see A288872(n) = A157867(n)/5^n. See a comment under A157866 for B[d,a](n).
%C A157883 (-1)^n*a(n) gives the numerators of the generalized Bernoulli numbers B[5,3](n); the denominators are A288872(n).
%C A157883 (End)
%H A157883 Vincenzo Librandi, <a href="/A157883/b157883.txt">Table of n, a(n) for n = 0..250</a>
%t A157883 Table[Numerator[BernoulliB[n, 2/5]], {n, 0, 50}] (* _Vincenzo Librandi_, Mar 16 2014 *)
%o A157883 (PARI) a(n) = numerator(subst(bernpol(n, x), x, 2/5)); \\ _Michel Marcus_, Jul 06 2017
%o A157883 (Python)
%o A157883 from sympy import bernoulli, Integer
%o A157883 def a(n): return bernoulli(n, Integer(2)/5).numerator
%o A157883 print([a(n) for n in range(51)]) # _Indranil Ghosh_, Jul 06 2017
%Y A157883 For denominators see A157867.
%Y A157883 Cf. A288872.
%K A157883 sign,frac
%O A157883 0,3
%A A157883 _N. J. A. Sloane_, Nov 08 2009